Synthesis of deuterated morpholine derivatives

ABSTRACT

The present invention is directed to a process for preparing a 2,26,6-d 4 -morpholine derivative represented by Structural Formula (I): 
     
       
         
         
             
             
         
       
     
     or a salt thereof.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/132,284, filed on Jun. 17, 2008. The entire teachings of the aboveapplication(s) are incorporated herein by reference.

BACKGROUND OF THE INVENTION

In certain instances, improvements in drug performance have beenreported as a result of incorporating deuterium into specific sites ofpharmaceutical agents. Site specific incorporation of deuterium withacceptable chemical and isotopic yields can be difficult and expensiveto achieve. Therefore, there is need to develop improved processes formaking pharmaceutical agents having site-specific deuteration which areeconomical and have high chemical and isotopic yields.

SUMMARY OF THE INVENTION

The present invention in one embodiment is directed to a novel processfor making 2,2,6,6-d₄ morpholine derivatives. The process comprisesreacting a compound of Formula (II) with an acid to form the compound ofFormula (I) or a salt thereof:

wherein:

R¹ is —H, —OH, —NO, —NH₂, —NHR^(a), —N(R^(a))₂, —C(═O)NR^(c)R^(d),—C(═O)OR^(g), -phthalimido, —SO₂—R^(b), or a group selected from alkyl,aryl, heteroaryl, aralkyl, heteroaralkyl, cycloalkyl, heterocycloalkyl,cycloalkylalkyl, and heterocycloalkylalkyl wherein the alkyl, aryl,heteroaryl, aralkyl, heteroaralkyl, cycloalkyl, heterocycloalkyl,cycloalkylalkyl, and heterocycloalkylalkyl are each independentlyoptionally substituted with one or more groups selected from halogen,C₁₋₆ alkyl, —OR^(e), —C(═O)OR^(e), —C(═O)R^(e), —NO₂, —CN, —NH₂,—NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(e), —C(═O)NR^(c)R^(d), —S(O)R^(e),—S(O)₂R^(e), —SR^(e), and —SO₂NR^(c)R^(d), wherein each C₁₋₆ alkyl isoptionally substituted with one or more groups selected from halogen,C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆ haloalkoxy;

each R^(a) is independently an alkyl optionally substituted withhalogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl or C₁₋₆haloalkoxy;

R^(b) is alkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl, each ofwhich is optionally substituted with one or more groups selected fromhalogen, C₁₋₆ alkyl, —OR^(e), —C(═O)OR^(e), —C(═O)R^(e), —NO₂, —CN,—NH₂, —NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(e), —C(═O)NR^(c)R^(d),—S(O)R^(e), —S(O)₂R^(e), —SR^(e), and —SO₂NR^(c)R^(d), wherein each C₁₋₆alkyl is optionally substituted with one or more groups selected fromhalogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆haloalkoxy;

R^(c) and R^(d) are each independently —H or alkyl optionallysubstituted with one or more groups selected from halogen, C₁₋₆ alkyl,—OR^(e), —C(═O)OR^(e), —C(═O)R^(e), —NO₂, —CN, —NH₂, —NHR^(a),—N(R^(a))₂, —NR^(c)C(═O)R^(e), —C(═O)NR^(c)R^(d), —S(O)R^(e),—S(O)₂R^(e), —SR^(e), and —SO₂NR^(c)R^(d), wherein each C₁₋₆ alkyl isoptionally substituted with one or more groups selected from halogen,C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆ haloalkoxy;

R^(e) is —H or alkyl optionally substituted with one or more groupsselected from halogen, C₁₋₆ alkyl, —OR^(f), —C(═O)OR^(f), —C(═O)R^(f),—NO₂, —CN, —NH₂, —NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(f),—C(═O)NR^(c)R^(d), —S(O)R^(f), —S(O)₂R^(f), —SR^(f), and—SO₂NR^(c)R^(d), wherein each C₁₋₆ alkyl substituent is optionallysubstituted with one or more groups selected from halogen, C₁₋₆ alkyl,C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆ haloalkoxy;

R^(f) is alkyl, cycloalkyl, heterocycloalkyl, aryl or heteroaryl;

R^(g) is alkyl optionally substituted with one or more groups selectedfrom halogen, C₁₋₆ alkyl, —OR^(f), —C(═O)OR^(f), —C(═O)R^(f), —NO₂, —CN,—NH₂, —NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(f), —C(═O)NR^(c)R^(d),—S(O)R^(f), —S(O)₂R^(f), —SR^(f), and —SO₂NR^(c)R^(d), wherein each C₁₋₆alkyl substituent is optionally substituted with one or more groupsselected from halogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl andC₁₋₆ haloalkoxy;

and

R⁴, R^(4′), R⁵ and R^(5′) are each independently —H or C₁₋₄ alkyloptionally substituted with one or more halogen, C₁₋₆ alkyl, C₁₋₆alkoxy, —OH, C₁₋₆ haloalkyl, or C₁₋₆ haloalkoxy.

In another embodiment, the present invention is directed to a syntheticintermediate for preparing 2,2,6,6-d₄ morpholine derivatives. In anexample of this embodiment, the present invention is directed to asynthetic intermediate for preparing the deuterated linezolid ofcompound 10.

Such intermediates include the compounds of Formulas (I), (Ia), (Ib),and (Ic) and the compounds of Formulas (II), (IIa), and (IIb):

or a salt thereof, wherein each of R¹, R⁴, R^(4′), R⁵, and R^(5′) are asdefined above.

In another embodiment, the present invention is directed to apharmaceutical composition comprising a pharmaceutically acceptablecarrier and the deuterated linezolid of compound 10, or apharmaceutically acceptable salt thereof, wherein the deuteriumenrichment at each position designated as deuterium in compound 10 or apharmaceutically acceptable salt thereof is at least about 75%.

In another embodiment, the present invention is directed to a method oftreating a bacterial infection or a fungal disorder in a subject in needthereof comprising the step of administering to the subject an effectiveamount of compound 10 or a pharmaceutically acceptable salt thereof,wherein the deuterium enrichment at each position designated asdeuterium in compound 10 or a pharmaceutically acceptable salt thereofis at least about 75%.

Another embodiment of the present invention is directed to use ofcompound 10 or a pharmaceutically acceptable salt thereof for themanufacture of a medicament for treating a bacterial infection or afungal disorder in a subject in need of the treatment, wherein thedeuterium enrichment at each position designated as deuterium incompound 10 or a pharmaceutically acceptable salt thereof is at leastabout 75%.

Another embodiment of the present invention is directed to compound 10or a pharmaceutically acceptable salt thereof for use in treating abacterial infection or a fungal disorder in a subject in need thereof,wherein the deuterium enrichment at each position designated asdeuterium in compound 10 or a pharmaceutically acceptable salt thereofis at least about 75%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C depict concentration-time curve of linezolid in male ratsfollowing intravenous and oral administration of linezolid incombination with compound 10. FIG. 1A is a plot showing plasmaconcentration of linezolid versus time following intravenousadministration of linezolid and compound 10 for each male rat tested.FIG. 1B is a plot showing plasma concentration of linezolid versus timefollowing oral administration of linezolid and compound 10 for each malerat tested. FIG. 1C is plot showing mean plasma concentration oflinezolid versus time following intravenous and oral administration oflinezolid and compound 10. The No. designation in FIGS. 1A and 1B referto the number given to the test rat.

FIGS. 2A-2C depict concentration-time curve of compound 10 in male ratsfollowing intravenous and oral administration of compound 10 incombination with linezolid. FIG. 2A is a plot showing plasmaconcentration of compound 10 versus time following intravenousadministration of compound 10 for each male rat tested and linezolid.FIG. 2B is a plot showing plasma concentration of linezolid versus timefollowing oral administration of compound 10 and linezolid for each malerat tested. FIG. 2C is plot showing mean plasma concentration oflinezolid versus time following intravenous and oral administration ofcompound 10 and linezolid. The No. designation in FIGS. 2A and 2B referto the number given to the test rat.

FIG. 3 is a plot showing mean plasma concentration of linezolid (

) and compound 10 (

) versus time following intravenous administration of linezolid andcompound 10.

FIG. 4 is a plot showing mean plasma concentration of linezolid (

) and compound 10 (

) versus time following oral administration of linezolid and compound10.

FIGS. 5A and 5B depict inhibition of mtDNA-encoded protein synthesis bylinezolid (5A) and compound 10 (5B). The ratio of mtDNA encoded proteinover nuclear DNA encoded protein was plotted against the concentrationof tested compounds.

DETAILED DESCRIPTION OF THE INVENTION

The following definitions are used throughout the specification.

Unless otherwise stated, when a position is designated specifically as“H” or “hydrogen”, the position is understood to have hydrogen at itsnatural abundance isotopic composition. Also unless otherwise stated,when a position is designated specifically as “D” or “deuterium”, theposition is understood to have deuterium at an abundance that is atleast 3500 times greater than the natural abundance of deuterium, whichis 0.015% (i.e., at least 52.5% incorporation of deuterium).

“Halo” or “halogen” means chloro, bromo, or fluoro.

“Alkyl”, unless otherwise designated, means an aliphatic hydrocarbongroup which may be straight-chain or branched having 1 to 15 carbonatoms. Preferred alkyl groups have 1 to 12 carbon atoms. Even morepreferred alkyl groups are C₁₋₆ alkyl groups, which are saturatedstraight-chain or branched hydrocarbons having one to six carbon atoms.A “lower alkyl” group is a C₁₋₄ alkyl group. “Branched” means that oneor more lower alkyl groups such as methyl, ethyl or propyl are attachedto a linear alkyl chain. Exemplary alkyl groups include methyl, ethyl,n-propyl, i-propyl, n-butyl, t-butyl, n-pentyl, 3-pentyl, heptyl, octyl,nonyl, decyl and dodecyl; preferred are methyl, and i-propyl.

“Aryl” means an aromatic carbocyclic radical containing 6 to 10 carbonatoms. Exemplary aryl groups include phenyl or naphthyl.

“Heteroaryl” means 5-12 membered aromatic monocyclic or multicyclichydrocarbon ring system in which one or more of the carbon atoms in thering system is or are element(s) other than carbon, for examplenitrogen, oxygen or sulfur. Exemplary heteroaryl groups includepyrazinyl, furanyl, thienyl, pyridyl, pyrimidinyl, isoxazolyl,isothiazolyl, pyridazinyl, 1,2,4-triazinyl, thiadiazolyl, oxadiazolyl,quinolinyl, and isoquinolinyl.

“Aralkyl” means an aryl-alkyl group in which the aryl and alkylcomponents are as previously described. Preferred aralkyls contain alower alkyl moiety. Exemplary aralkyl groups include benzyl and2-phenethyl.

“Heteroaralkyl” means a heteroaryl-alkyl group in which the heteroaryland alkyl components are as previously described.

“Cycloalkyl” means a non-aromatic mono- or multicyclic ring system of 3to 10 carbon atoms.

“Heterocycloalkyl” means a non-aromatic mono- or multicyclic hydrocarbonring system in which at least one of the carbon atoms in the ring systemis replaced by a heteroatom, for example nitrogen, oxygen or sulfur.Exemplary heterocycloalkyl groups include pyrrolidinyl, piperidinyl,tetrahydropyranyl, tetrahydrofuranyl, tetrahydrothiopyranyl, andtetrahydrothiofuranyl.

“Cycloalkylalkyl” means a group in which the cycloalkyl and alkylcomponents are as previously described.

“Heteroycloalkylalkyl” means a group in which the cycloalkyl and alkylcomponents are as previously described.

The term “compound,” when referring to a compound of this invention,refers to a collection of molecules having an identical chemicalstructure, except that there may be isotopic variation among theconstituent atoms of the molecules. Thus, it will be clear to those ofskill in the art that a compound represented by a particular chemicalstructure containing indicated deuterium atoms, will also contain lesseramounts of isotopologues having hydrogen atoms at one or more of thedesignated deuterium positions in that structure. The relative amount ofsuch isotopologues in a compound of this invention will depend upon anumber of factors including the isotopic purity of deuterated reagentsused to make the compound and the efficiency of incorporation ofdeuterium in the various synthesis steps used to prepare the compound.However, as set forth above the relative amount of such isotopologues intoto will be less than 49.9% of the compound. In other embodiments, therelative amount of such isotopologues in toto will be less than 47.5%,less than 40%, less than 32.5%, less than 25%, less than 17.5%, lessthan 10%, less than 5%, less than 3%, less than 1%, or less than 0.5% ofthe compound.

A Brønsted acid is a proton donor. A Lewis acid is an electron pairacceptor.

Examples of Bronsted and Lewis acids are well known to the skilledartisan, and are commercially available from a wide variety of sources.

Other definitions are set forth in the table below

HPLC High performance liquid chromatography Hr Hour Kg Kilogram LCLiquid chromatography L Liter LOQ Limit of quantitation ug or μgMicrogram mg Milligram mL Milliliter Min Minute MS Mass spectrometry NANot applicable

The present invention is directed to a process for preparing 2,2,6,6-d₄morpholine derivatives represented by Structural Formula (I):

or a salt thereof. Values and specific values for each variable inStructural Formula (I) are provided in the following paragraphs:

R¹ is —H, OH, —NO, —NH₂, —NHR^(a), —N(R^(a))₂, —C(═O)NR^(c)R^(d),—C(═O)OR^(g), -phthalimido, —SO₂—R^(b), or a group selected from alkyl,aryl, heteroaryl, aralkyl, heteroaralkyl, cycloalkyl, heterocycloalkyl,cycloalkylalkyl, heterocycloalkylalkyl wherein the alkyl, aryl,heteroaryl, aralkyl, heteroaralkyl, cycloalkyl, heterocycloalkyl,cycloalkylalkyl, and heterocycloalkylalkyl are each independentlyoptionally substituted with one or more groups selected from halogen,C₁₋₆ alkyl, —OR^(e), —C(═O)OR^(e), —C(═O)R^(e), —NO₂, —CN, —NH₂,—NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(e), —C(═O)NR^(c)R^(d), —S(O)R^(e),—S(O)₂R^(e), —SR^(e), and —SO₂NR^(c)R^(d), wherein each C₁₋₆ alkyl isoptionally substituted with one or more groups selected from halogen,C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆ haloalkoxy. In oneembodiment, R¹ is —H, optionally substituted alkyl, optionallysubstituted aryl, optionally substituted heteroaryl, optionallysubstituted aralkyl, —C(═O)NR^(c)R^(d), —C(═O)OR^(g), or —SO₂—R^(b). Inanother embodiment, R¹ is —H or optionally substituted benzyl, whereinthe benzyl is optionally substituted with one or more groups selectedfrom halogen, —OR^(e), —C(═O)OR^(e), —C(═O)R^(e), —NO₂, —CN, —NH₂,—NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(e), —C(═O)NR^(c)R^(d), —S(O)R^(e),—S(O)₂R^(e), —SR^(e), and —SO₂NR^(c)R^(d). In another embodiment, R¹ is—H or unsubstituted benzyl. In another embodiment, R¹ is an alkyl groupthat is optionally substituted with one or more groups selected fromhalogen, C₁₋₆ alkyl, C₁₋₆ haloalkyl, —OR^(e), —C(═O)OR^(e), —C(═O)R^(e),—NO₂, —CN, —NH₂, —NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(e),—C(═O)NR^(c)R^(d), —S(O)R^(e), —S(O)₂R^(e), —SR^(e), and—SO₂NR^(c)R^(d), wherein the C₁₋₆ alkyl and C₁₋₆ haloalkyl substitutentsare each further optionally substituted with one or more groups selectedfrom halogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆haloalkoxy.

R^(a), for each occurrence, is independently an alkyl optionallysubstituted with one or more groups selected from halogen, C₁₋₆ alkyl,C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆ haloalkoxy.

R^(b) is alkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl, each ofwhich is optionally substituted with one or more groups selected fromhalogen, C₁₋₆ alkyl, —OR^(e), —C(═O)OR^(e), —C(═O)R^(e), —NO₂, —CN,—NH₂, —NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(e), —C(═O)NR^(c)R^(d),—S(O)R^(e), —S(O)₂R^(e), —SR^(e), and —SO₂NR^(c)R^(d), wherein each C₁₋₆alkyl substitutent is optionally substituted with one or more groupsselected from halogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl andC₁₋₆ haloalkoxy.

R^(c) and R^(d) are each independently —H or an alkyl optionallysubstituted with one or more groups selected from halogen, C₁₋₆ alkyl,—OR^(e), —C(═O)OR^(e), —C(═O)R^(e), —NO₂, —CN, —NH₂, —NHR^(a),—N(R^(a))₂, —NR^(c)C(═O)R^(e), —C(═O)NR^(c)R^(d), —S(O)R^(e),—S(O)₂R^(e), —SR^(e), and —SO₂NR^(c)R^(d), wherein each C₁₋₆ alkylsubstituent is optionally substituted with one or more groups selectedfrom halogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆haloalkoxy.

R^(e) is alkyl optionally substituted with one or more groups selectedfrom halogen, C₁₋₆ alkyl, —OR^(f), —C(═O)OR^(f), —C(═O)R^(f), —NO₂, —CN,—NH₂, —NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(f), —C(═O)NR^(c)R^(d),—S(O)R^(f), —S(O)₂R^(f), —SR^(f), and —SO₂NR^(c)R^(d), wherein each C₁₋₆alkyl substituent is optionally substituted with one or more groupsselected from halogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl andC₁₋₆ haloalkoxy;

R^(f) is alkyl, cycloalkyl, heterocycloalkyl, aryl or heteroaryl;

R^(g) is —H or alkyl optionally substituted with one or more groupsselected from halogen, C₁₋₆ alkyl, —OR^(f), —C(═O)OR^(f), —C(═O)R^(f),—NO₂, —CN, —NH₂, —NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(f),—C(═O)NR^(c)R^(d), —S(O)R^(f), —S(O)₂R^(f), —SR^(f), and—SO₂NR^(c)R^(d), wherein each C₁₋₆ alkyl substituent is optionallysubstituted with one or more groups selected from halogen, C₁₋₆ alkyl,C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆ haloalkoxy; and

R⁴, R^(4′), R⁵ and R^(5′) are each independently —H, or C₁₋₄ alkyloptionally independently substituted with one or more halogen, C₁₋₆alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl or C₁₋₆ haloalkoxy.

In one embodiment, R^(e) is alkyl optionally substituted with one ormore groups selected from halogen, C₁₋₆ alkyl, —NO₂, —CN, —NH₂,—NHR^(a), —N(R^(a))₂, —C(═O)NR^(c)R^(d), and —SO₂NR^(c)R^(d), whereineach C₁₋₆ alkyl substituent is optionally substituted with one or moregroups selected from halogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆haloalkyl and C₁₋₆ haloalkoxy.

In one embodiment, R⁴, R^(4′), R⁵ and R^(5′) are all —H.

In one embodiment, the process of the invention comprises reacting acompound of Formula (II) with an acid to form the compound of Formula(I) or a salt thereof:

Typically the reaction is performed at a temperature in the range of100-200° C., such as 120-160° C., such as 140 to 150° C. over a timeranging from 1 to 24 hours, such as between 10 and 18 hours, such asbetween 16 and 18 hours.

In one embodiment, the compound of Formula (II), or a salt thereof, isprepared by reacting a compound of Formula (III) with a reducing agent:

wherein each R² is D, —OH, or —O(alkyl). For example, R² may be —OH or—O(alkyl). If R² is —O(alkyl), the alkyl group in —O(alkyl) isoptionally substituted with one or more groups selected from halogen,C₁₋₆ alkyl, —OR^(e), —C(═O)OR^(e), —C(═O)R^(e), —NO₂, —CN, —NH₂,—NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(e), —C(═O)NR^(c)R^(d), —S(O)R^(e),—S(O)₂R^(e), —SR^(e), and —SO₂NR^(c)R^(d), wherein each C₁₋₆ alkyl isoptionally substituted with one or more groups selected from halogen,C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆ haloalkoxy. In oneembodiment, R² is —O(C₁₋₃ alkyl). In another embodiment, R² is —OEt(Et=ethyl).

In one embodiment, the process for preparing the compound of Formula (I)comprises:

(a) reacting a compound of Formula (III) with a reducing agent to formthe compound of Formula (II); and (b) reacting the compound of Formula(II) with an acid to form the optionally substituted morpholinederivative of Formula (I) or a salt thereof.

In another embodiment, the process described above further comprises thestep of removing R¹ from a compound of Formula (I) when it is other than—H to form a morpholine derivative of Formula (Ia) or a salt thereof:

In a specific embodiment, R¹ for Reaction 3 is benzyl and the benzylgroup is removed under hydrogenation conditions. In one embodiment,reagents for removing R¹ from the compound of Formula (I) includehydrogen gas. In one embodiment, hydrogenation may be performed using ametal-based catalyst. More specifically, a palladium-based catalyst or aplatinum-based catalyst may be used. Suitable palladium-based catalystsare well-known to one skilled in the art. In one embodiment, thepalladium-based catalyst is Pd(OH)₂ on carbon. In another embodiment,the catalyst is an elemental palladium catalyst, such as Pd/C,Pd/alumina, or palladium black. A suitable platinum-based catalysts is,for example, an elemental platinum catalyst such as Pt/C.

In one embodiment, for any one of compounds of Structural Formulas (I),(Ia), (II) and (III), R⁴, R^(4′), R⁵ and R^(5′) are all —H.

In another embodiment, for any one of compounds of Structural Formulas(I), (II) and (III), R¹ is —H, an alkyl optionally substituted asdefined above, a benzyl optionally substituted as defined above,—SO₂R^(b), or —C(═O)NR^(c)R^(d).

In another embodiment, for any one of compounds of Structural Formulas(I), (II) and (III), R¹ is —H, an alkyl optionally substituted asdefined above, benzyl, or —SO₂R^(b). In another embodiment, R¹ is —H,benzyl or —SO₂R^(b). In a more specific embodiment, R¹ is benzyl,—SO₂-aryl or —SO₂-heteroaryl. In an even more specific embodiment, R¹ isbenzyl. In one aspect of this more specific embodiment, R¹ is benzyl;and R⁴, R^(4′), R⁵ and R^(5′) are all —H.

Acids that are suitable for Reaction 1 are well known to one skilled inthe art. The acid can be a Lewis acid or a Bronsted acid. Examples ofsuitable acid include, but not limited to, hydrochloric acid, sulfuricacid, phosphoric acid, trifluoroacetic acid, HBF₄, ZnCl₂ optionally witha co-solvent such as THF, toluenesulfonic acid optionally with aco-solvent such as toluene, and boron trifluoride etherate. In oneembodiment, the acid is an aqueous acid. More specifically, the acid issulfuric acid. Even more specifically, the acid is 70% sulfuric acid.

Suitable reducing agents for Reaction 2 are also well known to oneskilled in the art. Some examples of suitable reducing agents include,but are not limited to, diborane-d₆ (B₂D₆), DSiCl₃, Et₃SiD,diisobutylaluminum deuteride (DIBAL-D), LiAlD₄, LiBD₄, and NaBD₄. In oneembodiment, the reducing agent is selected from the group consisting ofLiAlD₄, LiBD₄, and NaBD₄. More specifically, the reducing agent isLiAlD₄.

The present invention is also directed to the compounds of Formulas (I),(Ia), (Ib), and (Ic) and the synthetic intermediates of Formulas (II),(IIa), and (IIb):

or a salt thereof, wherein each of R¹, R⁴, R^(4′), R⁵, and R^(5′) are asdefined above.

In one embodiment, R¹ in any one of Structural Formulas (I), (Ic), (II)and (IIb) is benzyl, —SO₂-aryl, or —SO₂-heteroaryl, each of which isoptionally substituted. In one embodiment, R¹ in any one of StructuralFormulas (I), (Ic), (II) and (IIb) is —H or benzyl.

As an example, the present invention is directed to compounds 3 and 3aand to synthetic intermediate, compound 2.

or a salt of any of the foregoing.

The process of the present invention can be used to prepare deuteratedversion of morpholine-containing pharmaceutical agents. Suchpharmaceutical agents include, but are not limited to, xamoterol,xamoterol fumarate, mycophenolate mofetil, rocuronium, rocuroniumbromide, moclobemide, landiolol, linezolid, emorfazone, moricizine,moricizine hydrochloride, timolol, timolol maleate, molsidomine,gefitinib, pinaverium, pinaverium bromide, nimorazole, linsidomine,morniflumate, rivaroxaban, aprepitant, fosaprepitant, radafaxine, andpharmaceutical acceptable salts thereof.

As used herein, “morpholine-containing pharmaceutical agents” refers toany pharmaceutical agents that contain one or more morpholine moiety.The morpholine moiety can have one or more substituents on themorpholine ring.

In one embodiment, the process of the present invention can be used tomake deuterated linezolid comprising a morpholine moiety represented bythe following structural formula:

Examples of deuterated linezolid of the present invention arerepresented by the following structural formulas:

or a pharmaceutically acceptable salt of either of the foregoing.

The deuterated linezolid 10 can be prepared according to Scheme 2described below.

One embodiment of the present invention is directed to deuteratedlinezolid 10 and the synthetic intermediates represented by thefollowing structural formulas:

or a salt of any of the foregoing.

In one embodiment, the deuterium enrichment at each position for any oneof the compounds represented by Structural Formulas (I)-(Ic),(II)-(IIb), (2), (3), (3a), (4)-(11) is at least about 70%, at leastabout 75%, at least about 80%, at least about 85%, at least about 90%,at least about 95%, at least about 97%, at least about 97.5%, at leastabout 99.0% or at least about 99.5%. The percentage for deuteriumenrichment refers to mole percentage. When any of these compounds areanalyzed by ¹H NMR, the lack of a visible signal corresponding to theprotons alpha to the oxygen indicates deuterium enrichment at thosepositions of at least 95%.

As used herein, salts include acid salts and base salts. For example,acid salts of a compound of the present invention containing an amine orother basic group can be obtained by reaction of the compound with asuitable organic or inorganic acid resulting in anionic salt. In oneembodiment, acid salts of the present invention are pharmaceuticallyacceptable salts. Such pharmaceutically acceptable salts include, butnot limited to acetate, benzenesulfonate, benzoate, bicarbonate,bitartrate, bromide, calcium edetate, camsylate, carbonate, chloride,citrate, dihydrochloride, edetate, edisylate, estolate, esylate,fumarate, glyceptate, gluconate, glutamate, glycollylarsanilate,hexylresorcinate, hydrobromide, hydrochloride, hydroxynaphthoate,iodide, isethionate, lactate, lactobionate, malate, maleate, mandelate,mesylate, methylsulfate, mucate, napsylate, nitrate, pamoate,pantothenate, phosphate/diphosphate, polygalacturonate, salicylate,stearate, subacetate, succinate, sulfate, tannate, tartrate, teoclate,tosylate, and triethiodide salts. Non-pharmaceutically acceptable saltsare also included in the present invention, such as trifluoroacetic acidsalt.

Salts of the compounds of the present invention containing a carboxylicacid or other acidic functional group can be prepared by reacting with asuitable base. In one embodiment, base salts of the present inventionare pharmaceutically acceptable salts. Such a pharmaceuticallyacceptable salt may be made with a base which affords a pharmaceuticallyacceptable cation, which includes alkali metal salts (especially sodiumand potassium), alkaline earth metal salts (especially calcium andmagnesium), aluminum salts and ammonium salts, as well as salts madefrom physiologically acceptable organic bases such as trimethylamine,triethylamine, morpholine, pyridine, piperidine, picoline,dicyclohexylamine, N,N′-dibenzylethylenediamine, 2-hydroxyethylamine,bis-(2-hydroxyethyl)amine, tri-(2-hydroxyethyl)amine, procaine,dibenzylpiperidine, dehydroabietylamine, N,N′-bisdehydroabietylamine,glucamine, N-methylglucamine, collidine, quinine, quinoline, and basicamino acids such as lysine and arginine.

A “pharmaceutically acceptable salt” means any non-toxic salt that, uponadministration to a recipient, is capable of providing, either directlyor indirectly, a compound of this invention.

In another embodiment, a pharmaceutical composition comprising adeuterated linezolid of the present invention further comprises a secondtherapeutic agent. The second therapeutic agent includes any compound ortherapeutic agent known to have or that demonstrates advantageousproperties when administered with an antimicrobial compound, inparticular, in anti-microbial therapy, combination therapy with otheranti-microbial and/or anti-inflammatory agents is envisaged. Combinationtherapies according to the present invention thus include theadministration of a deuterated linezolid of the present invention (i.e.,a deuterated linezolid comprising a 2,2,6,6-d₄ morpholinyl moiety andhaving a deuterium enrichment at each position designated as deuteriumof at least about 70%) at least one compound of formula I or Ia, as wellas optional use of other anti-microbial agents and optional use ofcyclooxygenase inhibitors, particularly selective inhibitors ofcyclooxygenase-2. Other anti-microbial therapies and anti-inflammatoryagents are described for instance in International Publication Nos. WO01/34128 and WO 03/061704, which applications are incorporated byreference to the extent that they disclose combinations ofanti-microbial and anti-inflammatory therapies.

Examples of second therapeutic agents that may be formulated with adeuterated linezolid of this invention include, but are not limited to,gentamicin, tobramycin, aztreonam, cefazolin, ceftazidime, piperacillin,ciprofloxacin, ofloxacin, levofloxacin, celecoxib, and rofecoxib.

In the pharmaceutical compositions of the invention, the compound of thepresent invention is present in an effective amount. As used herein, theterm “effective amount” refers to an amount which, when administered ina proper dosing regimen, is sufficient to treat (e.g. reduce orameliorate the severity, duration or progression of the target disorder,prevent the advancement of the target disorder, cause the regression ofthe target disorder, or enhance or improve the prophylactic ortherapeutic effect(s) of another therapy) the target disease ordisorder.

The interrelationship of dosages for animals and humans (based onmilligrams per meter squared of body surface) is described in Freireichet al., (1966) Cancer Chemother Rep 50: 219. Body surface area may beapproximately determined from height and weight of the patient. See,e.g., Scientific Tables, Geigy Pharmaceuticals, Ardsley, N.Y., 1970,537. An effective amount of a compound of this invention can range fromabout 50 mg to about 2000 mg every 24 hours, if appropriate in the formof several individual doses. In one embodiment the effective amount of acompound of this invention ranges from about 250 mg to about 1250 mgevery 24 hours in the form of a single dosage or two separate dosages ofabout 125 mg to about 625 mg each given every 12 hours. In anotherembodiment the effective amount of a compound of this invention rangesfrom about 750 mg to about 1250 mg every 24 hours in the form of asingle dosage or two separate dosages of about 375 mg to about 625 mgeach given every 12 hours. In still another embodiment the effectiveamount of a compound of this invention ranges from about 450 mg to about1200 mg every 24 hours in the form of a single dosage or two separatedosages of about 225 mg to about 625 mg each given every 12 hours. In amore specific embodiment the effective amount of a compound of thisinvention ranges from about 450 mg to about 750 mg every 24 hours in theform of a single dosage or two separate dosages of about 225 mg to about375 mg each given every 12 hours. Other ranges of a compound of thisinvention that fall within or between any of the above-recited rangesare also within the scope of the invention. Effective doses will alsovary, as recognized by those skilled in the art, depending on thediseases treated, the severity of the disease, the route ofadministration, the sex, age and general health condition of thepatient, excipient usage, the possibility of co-usage with othertherapeutic treatments such as use of other agents and the judgment ofthe treating physician.

The milligram amounts of compounds present in the pharmaceuticalcompositions of the present invention and for use in the methods of thepresent invention represent the amount of free base compound. It will beunderstood that the use of pharmaceutical salts of the compounds of thepresent invention will require that the stated amounts be increased sothat a mole equivalent of the free base compound is used.

For pharmaceutical compositions that comprise a second therapeuticagent, an effective amount of the second therapeutic agent is betweenabout 20% and 100% of the dosage normally utilized in a monotherapyregime using just that agent. Preferably, an effective amount is betweenabout 70% and 100% of the normal monotherapeutic dose. The normalmonotherapeutic dosages of these second therapeutic agents are wellknown in the art. See, e.g., Wells et al., eds., PharmacotherapyHandbook, 2nd Edition, Appleton and Lange, Stamford, Conn. (2000); PDRPharmacopoeia, Tarascon Pocket Pharmacopoeia 2000, Deluxe Edition,Tarascon Publishing, Loma Linda, Calif. (2000), each of which referencesare entirely incorporated herein by reference.

It is expected that some of the second therapeutic agents referencedabove will act synergistically with the compounds of this invention.When this occurs, its will allow the effective dosage of the secondtherapeutic agent and/or the compound of this invention to be reducedfrom that required in a monotherapy. This has the advantage ofminimizing toxic side effects of either the second therapeutic agent ofa compound of this invention, synergistic improvements in efficacy,improved ease of administration or use and/or reduced overall expense ofcompound preparation or formulation.

According to another embodiment, the invention provides a method oftreating a subject suffering from or susceptible to a disease that isbeneficially treated by linezolid comprising the step of administeringto said subject an effective amount of a deuterated linezolid or apharmaceutical composition of this invention. Such diseases are wellknown in the art and include for instance, the treatment or preventionof a variety of disease states typically treated by antimicrobialtherapy (e.g., infection, fungal disorders). The deuterated linezolid ofthis invention, therefore, have utility in the treatment of disordersincluding those mediated by Gram-positive bacteria and certainGram-negative and anaerobic bacteria.

In one embodiment, the invention provides a method of treating a subjectsuffering from or susceptible to an infection caused by a bacteriaselected from Enterococcus faecium, Staphylococcus aureus, Streptococcusagalactiae, Streptococcus pneumoniae, Streptococcus pyrogenes,Enterococcus faecalis, Staphylococcus epidermidis, Staphyloccocushaemolyticus, and Pasteurella multocida,

In another embodiment, the invention provides a method of treating asubject suffering from or susceptible to a disease or disorder (orsymptoms thereof) selected from a Gram-positive bacterial infection,Vancomycin-resistant Enterococcus faecium infection; nosocomialpneumonia due to Staphylococcus aureus and Streptococcus pneumoniae;complicated skin and skin structure infections caused by Staphylococcusaureus, Streptococcus pyogenes, or Streptococcus agalactiae;uncomplicated skin and skin structure infections caused byStaphylococcus aureus or Streptococcus pyogenes; community-acquiredpneumonia caused by Streptococcus pneumoniae or Staphylococcus aureus;an infection of the eye; and tuberculosis.

In another embodiment, the invention provides a method of treating asubject suffering from diabetic foot infections, nocardiosis,endophthalmitis, keratitis, conjunctivitis, or impetigo.

In another embodiment, the invention provides a method of treating asubject suffering from or susceptible to a disease or disorder (orsymptoms thereof) selected from a Gram-positive bacterial infection,Vancomycin-resistant Enterococcus faecium infection; nosocomialpneumonia due to Staphylococcus aureus and Streptococcus pneumoniae;complicated skin and skin structure infections caused by Staphylococcusaureus, Streptococcus pyogenes, or Streptococcus agalactiae;uncomplicated skin and skin structure infections caused byStaphylococcus aureus or Streptococcus pyogenes; and community-acquiredpneumonia caused by Streptococcus pneumoniae or Staphylococcus aureus.

In another embodiment, the invention provides a method of treating apatient suffering from or susceptible to a bacterial infectioncomprising the step of administering to the patient in need thereof overa 24 hour period between about 450 mg and about 750 mg of a deuteratedlinezolid of this invention. In another embodiment the patient isadministered between 450 mg and 700 mg of a deuterated linezolid of thepresent invention.

In another embodiment, the above method of treatment comprises thefurther step of co-administering to the patient one or more secondtherapeutic agents. The choice of second therapeutic agent may be madefrom any second therapeutic agent known to be useful forco-administration with linezolid.

In a specific embodiment, the combination therapies of this inventioninclude co-administering a deuterated linezolid of the present inventionand a second therapeutic agent selected from gentamicin, tobramycin,aztreonam, cefazolin, ceftazidime, piperacillin, ciprofloxacin,ofloxacin, levofloxacin, celecoxib, and rofecoxib.

Example 1 Synthesis of 2,2,6,6-d₄-Morpholine (3a)

Step 1. 2,2′-(Benzylazanediyl)bis(1,1-d₂-ethanol) (2). To a solution ofdiethyl benzyliminodiacetate (1, 55.0 g, 196.9 mmol) in anhydroustetrahydrofuran (500 mL) at 0° C. was added lithium aluminum deuteride(16.5 g, 393.8 mmol, Cambridge Isotopes, 98 atom % D) in portions withinternal temperature below 10° C. After addition the reaction wasstirred overnight at room temperature and then quenched sequentiallywith water (16.5 mL), 15 wt % sodium hydroxide (16.5 mL), and water(49.5 mL) at 0° C. The suspension was stirred 2 hours at roomtemperature, filtered over celite cake, and washed with THF (400 mL).The filtrate was evaporated in vacuo to give 2 (36.5 g, 93%) as a paleyellow oil.

Step 2. N-benzyl-2,2,6,6-d₄-morpholine (3). A solution of 2 (36.5 g,183.4 mmol) in 70% sulfuric acid (138 mL) was heated in a sealed tube at150° C. for 16 hours, cooled to room temperature, and slowly poured ontocrushed ice (300 g). The resulting mixture was slowly basified to pH 9with solid potassium carbonate and mixed with EtOAc (500 mL). Thesuspension was filtered over a celite cake and washed with EtOAc (400mL). For the filtrate the two layers were split and the aqueous layerwas extracted with EtOAc (2×300 mL). The combined organic layers weredried over sodium sulfate and evaporated in vacuo to give 3 (31.6 g,95%) as lightly tan oil. The signal corresponding to the protons alphato the oxygen was not visible in the ¹H NMR spectrum performed on aVarian Mercury 300 MHz instrument. The absence of the signal indicatesthat less than 5% of hydrogen is present.

Step 3. 2,2,6,6-d₄-Morpholine (3a). A solution of (3, 31.6 g) inmethanol (300 mL) was shaken under hydrogen (30 psi) with Pd(OH)₂ oncarbon (6.3 g) as catalyst until no further hydrogen was consumed. Thereaction mixture was filtered over a celite cake and washed withmethanol (400 mL). The filtrate was evaporated at 25° C. to give 3a as apale yellow oil in quantitative yield. The signal corresponding to theprotons alpha to the oxygen was not visible in the ¹H NMR spectrumperformed on a Varian Mercury 300 MHz instrument. The absence of thesignal indicates that less than 5% of hydrogen is present.

Example 2 Synthesis of(S)—N-((3-(3-Fluoro-4-(2,2,6,6-d₄-morpholino)phenyl)-2-oxooxazolidin-5-yl)methyl)acetamide(10)

Step 1. 2,2,6,6-d₄-4-(2-Fluoro-4-nitrophenyl)morpholine (4). To asolution of 3,4-difluoronitrobenzene (12) (26.5 g, 166.3 mmol) anddiisopropylethylamine (76 mL, 436.5 mmol) in acetonitrile (350 mL) wasadded 3a (174.6 mmol). The reaction was stirred at reflux for 16 hours,then was concentrated in vacuo. The crude residue was taken up withwater (300 mL). The precipitate was filtered, washed with water (200 mL)and heptane (300 mL), and dried under vacuum at 40° C. for 5 hours togive 4 (34.8 g, 91%) as a bright yellow solid.

Step 2. 3-Fluoro-4-(2,2,6,6-d₄-morpholino)aniline (5). A solution of 4(34.8 g) in ethanol (400 mL) was shaken under hydrogen (30 psi) with 10wt % Pd/C (7.0 g, containing 50 wt % water) until no additional hydrogenwas consumed (ca. 3 hours). The reaction mixture was filtered overCelite and washed with ethanol (400 mL). The filtrate was concentratedin vacuo to give 5 (26.7 g, 85%) as a white solid.

Step 3.(R)-1-Chloro-3-(3-fluoro-4-(2,2,6,6-d₄-morpholino)phenylamino)propan-2-ol(6). To a solution of 5 (2.36 g, 11.8 mmol) in 2-propanol (30 mL) wasadded (R)-(−)-epichlorohydrin (1.2 g, 13.0 mmol). The reaction wasstirred at reflux for 15 hours and another 0.24 g (2.6 mmol) of(R)-(−)-epichlorohydrin was added. The reaction was stirred at refluxanother 6 hours and the solvent was removed to give 6 as an oil that wasused in the next step without further purification.

Step 4.(R)-5-(Chloromethyl)-3-(3-fluoro-4-(2,2,6,6-d₄-morpholino)phenyl)oxazolidin-2-one(7). A solution of 6 (ca. 11.8 mmol) and 1,1′-carbonyldiimidazole (2.68g, 16.5 mmol) in dichloromethane (100 mL) was stirred overnight at roomtemperature and concentrated to give a crude oil containing 7.

Step 5.(S)-2-((3-(3-Fluoro-4-(2,2,6,6-d₄-morpholino)phenyl)-2-oxooxazolidin-5-yl)methyl)isoindoline-1,3-dione(8). To a solution of 7 (ca. 11.8 mmol) in DMF (50 ml) was addedphthalimide potassium salt (2.84 g, 15.3 mmol). The reaction mixture washeated at 100° C. for 6 hours, cooled to room temperature, taken up withwater (100 mL), and extracted with MTBE (3×100 mL). The combined organiclayers were washed with brine (2×200 mL), dried over sodium sulfate, andconcentrated in vacuo. The crude solid was triturated with MTBE (100 mL)to give 8 (3.3 g, 66% for 3 steps) as a white solid.

Step 6.(S)-5-(Aminomethyl)-3-(3-fluoro-4-(2,2,6,6-d₄-morpholino)phenyl)oxazolidin-2-one(9). A solution of 8 (3.3 g, 7.68 mmol) and hydrazine monohydrate (2.07g, 42.3 mmol) in methanol (40 mL) was stirred at reflux for 1 hour. Thereaction mixture was concentrated in vacuo, taken up with water (100mL), and extracted with dichloromethane (3×100 mL). The combine organiclayers were washed with water (150 mL), dried over sodium sulfate, andconcentrated in vacuo to give 9 (2.16 g) as a tan oil in quantitativeyield.

Step 7.(S)—N-((3-(3-Fluoro-4-(2,2,6,6-d₄-morpholino)phenyl)-2-oxooxazolidin-5-yl)methyl)acetamide(10). To a solution of 9 (2.16 g, 7.22 mmol) in toluene at roomtemperature was added acetic anhydride (2 mL, 20.9 mmol). The reactionmixture was warmed at 35° C. for 5 minutes and then stirred overnight atambient temperature. The reaction mixture was cooled to 0° C., filtered,washed with toluene, and dried at 40° C. for 4 hours to give 10 (1.2 g,49%) as a white solid. The signal corresponding to the protons alpha tothe oxygen is not visible in the ¹H NMR spectrum.

Example 3 Pharmacokinetic Study in Rats Materials and Methods

18.08 mg of linezolid and 10.01 mg of compound 10 were dissolved in 10%DMI, 15% Ethanol, 35% PG, and 40% D5W independently to yield a finalconcentration at 10 mg/mL (pH ˜6). The combo dose was prepared by mixingboth by 1:1 to yield a concentration of 5 mg/mL for each compound (pH˜6) for intravenous and oral administration. The obtained solution wasclear and colourless. The concentrations of linezolid and compound 10 ineach individual dose were confirmed by HPLC method.

Male Sprague Dawley rats (body weight: 170 g to 220 g) were used in thisstudy. Before the pharmacokinetic studies, animals were randomlyassigned to the treatment groups. The treatment schedules are shown inTable 1.

TABLE 1 Experimental Design Target No. of Target Target Dose Dose MaleTest Article Dose Dose Level Concentration Volume Rats Test ArticleFormulation Route (mg/kg) (mg/mL) (mL/kg) 3 linezolid + 10% DMI/15% IV 5mg/kg 5 mg/mL for 1 compound 10 Ethanol/35% for each each PG/40% D5W 3linezolid + 10% DMI/15% PO 5 mg/kg 5 mg/mL for 1 compound 10 Ethanol/35%for each each PG/40% D5W

Blood samples were collected by retro-orbital at 0 (pre-dose) and 0.083,0.25, 0.5, 1, 2, 4, 6, 8, 10, 12, and 24 hours post-dose. The plasmasamples and the dose formulation were stored at −20° C. untilbioanalysis.

Sample Analysis

The concentrations of linezolid and compound 10 in plasma weredetermined using a high performance liquid chromatography/massspectrometry (HPLC/MS/MS) method.

LC-MS/MS Apparatus

The LC system comprised an Agilent (Agilent Technologies Inc. USA)liquid chromatograph equipped with an isocratic pump (1100 series), anautosampler (1100 series) and a degasser (1100 series). Massspectrometric analysis was performed using an API3000(triple-quadrupole) instrument from AB Inc (Canada) with an ESIinterface. The data acquisition and control system were created usingAnalyst 1.4 software from ABI Inc.

Other equipment: XW-80A Vortex mixer (Shanghai); TGL-16B high speedcentrifuge (Shanghai), Millipore Academic Ultrapure-water generatingsystem.

Internal Standard (Quetiapine) was a gift from Shanghai Institute ofPharmaceutical Industry. Acetonitrile and methanol (Tedia Inc, USA) wereHPLC grade. All other solvents and chemicals were analytical grade orbetter.

LC-MS/MS Conditions Chromatographic Conditions

Column: Phenomenex Gemini, C6-pheny, 5 μm, (50 mm×4.6 mm)Mobile phase: 0.1% Formic acid: Methanol=10: 90Elution rate: 1000 μL/minColumn temperature: 25° C.Injection volume: 5 μL

Mass

Scan type: Positive MRMIon source: Turbo spray Ionization model: ESI

Nebulize gas: 8 L/min Curtain gas: 8 L/min Collision gas: 4 L/min

Ionspray voltage: 4500 v; Temperature: 450° C.

Other Parameters:

Drug name Q1 Q3 Dell time DP (v) FP (v) EP (v) CE (v) CXP (v) Linezolid338.07 296.27 200 ms 61 160 10 27 20 compound 10 342.17 300.19 200 ms 56170 10 27 20 Quetiapine 384.2 253.2 200 ms 50 200 10 31 15

Preparation of Standard Stock Solution

A stock solution of linezolid and compound 10 was prepared by dissolvingthe drug in methanol to yield a final concentration of 200 μg/mL,respectively. Then proper volume of these two solutions were transferredinto one flask, and diluted to the mark with methanol to make a mixtureof two compounds with the same concentration of 25 μg/mL. An aliquot ofthis mixture was diluted using methanol to get a series of workingsolutions of 25, 50, 250, 500, 2500, 5000, and 25000 ng/mL. Sevencalibration standard samples containing 5000, 1000, 500, 100, 50, 10,and 5 ng/mL were obtained by adding 20 μL working solution preparedabove into seven Eppendorff tubes containing 100 μL blank plasma. QCsamples were prepared by spiking 100 μL blank plasma with 20 μL workingsolutions of 20000, 4000, and 40 ng/mL to yield final concentration of4000, 800, and 8 ng/mL.

Stock solution of Quetiapine (internal standard, IS) was prepared bydissolving the drug in methanol to a final concentration of 200 μg/mL.This solution was diluted with methanol to yield a final concentrationof 50 ng/mL.

Plasma Sample Process

Plasma samples (0.1 mL) were transferred to Eppendorff tube, then 20methanol, and 300 μL IS solution (50 ng/mL) were added to it. AfterVortexing for 1 min and centrifuging for 5 min at 15,000 rpm, 5 μL ofsupernatant was injected into LC/MS/MS.

Method Validation Results Specificity

The chromatographic conditions showed that the blank plasma had nointerference to the test compounds and IS determination.

Calibration Curve

The analytical curves were constructed using seven nonzero standardsranging from 5 to 5000 ng/mL. A blank sample (matrix sample processedwithout internal standard) was used to exclude contamination. The linearregression analysis of linezolid and compound 10 were performed byplotting the peak area ratio (y) against the concentration (x) in ng/mLfor linezolid or compound 10, respectively. The linearity of therelationship between peak area ratio and concentration were demonstratedby the correlation coefficients (R) obtained for the linear regressionsof linezolid and compound 10.

Intra-Assay Accuracy

The intra-assay accuracy results (ranged from 83.54% to 106.38% forlinezolid, and 94.00% to 113.32% for compound 10) showed that the methodis reliable.

Data Analysis Pharmacokinetic Data Analysis

The concentrations in plasma below the limit of quantitation (LOQ=5ng/mL) were designated as zero. The pharmacokinetic data analysis wasperformed using noncompartmental analysis modules in WinNonlin2.0. Thebioavailability was calculated as F(%)=(Dose_(iv)×AUC_(oral(0-∞)))/(Dose_(oral)×AUC_(iv(0-∞)))*100%.

Results and Discussion

Pharmacokinetics of Linezolid after Combinatory Administration

The individual and average concentration-time data of linezolidfollowing intravenous and oral administration linezolid in combinationwith compound 10 are listed in Table 2 and shown in FIGS. 1A-1C.Selected noncompartmental pharmacokinetic parameters followingintravenous and oral dose are listed in Table 3.

TABLE 2 Plasma Concentration of Linezolid in Male Rats FollowingIntravenous and Oral Administration in Combo with Compound 10 Time (hr)Plasma Concentration (ng/mL) IV-5 mg/kg R7 R8 R9 Mean SD 0 BLQ BLQ BLQNA NA 0.083 6324.03 5309.66 5983.54 5872.41 516.24 0.25 4352.05 4727.024742.46 4607.18 221.08 0.5 3323.69 3959.46 4045.58 3776.24 394.28 12919.08 2636.07 2835.48 2796.88 145.40 2 1361.81 1350.43 1596.24 1436.16138.75 4 278.33 320.60 361.30 320.08 41.49 6 58.01 61.51 69.63 63.055.96 8 15.53 26.06 16.75 19.45 5.76 10 4.46 7.24 7.29 6.33 1.62 12 0 0 0NA NA 24 0 0 0 NA NA PO-5 mg/kg R10 R11 R12 Mean SD 0 0 0 0 NA NA 0.0833117.08 872.70 829.97 1606.58 1308.30 0.25 3594.56 1764.67 1099.442152.89 1292.07 0.5 3266.77 2142.20 1132.83 2180.60 1067.49 1 2544.561964.34 1169.57 1892.82 690.28 2 1424.06 1728.58 860.03 1337.56 440.69 4382.80 789.74 664.96 612.50 208.48 6 70.20 184.51 420.25 224.99 178.50 821.39 46.16 146.45 71.33 66.22 10 0.00 19.47 40.28 19.92 20.14 12 0.000.00 5.15 1.72 2.97 24 0.00 0.00 0.00 NA NA SD: Standard deviation; NA:Not applicable, or failed to collect samples.

TABLE 3 Selected Pharmacokinetics Parameters of Linezolid in RatsFollowing Intravenous and Oral Administration in Combo with Compound 10AUC_((0-t)) AUC_((0-∞)) MRT_((0-∞)) t_(1/2z) T_(max) V_(z) CL_(z)C_(max) F μg/L * hr μg/L * hr hr hr hr L/kg L/hr/kg μg/L % IV-5 mg/kg R18200.53 8207.49 1.28 1.08 0.083 0.95 0.61 6324.03 R2 8193.82 8204.531.34 1.03 0.083 0.90 0.61 5309.66 R3 8956.18 8966.61 1.36 0.99 0.0830.80 0.56 5983.54 mean 8450.17 8459.54 1.33 1.03 0.083 0.88 0.59 5646.60SD 438.23 439.14 0.04 0.05 0 0.08 0.03 476.51 PO-5 mg/kg R4 7361.117366.21 1.54 0.96 0.25 NA NA 3594.56 87.02 R5 7429.44 7434.26 2.28 1.040.5 NA NA 2142.20 87.82 R6 5474.04 5480.19 3.17 0.83 1 NA NA 1169.5764.71 mean 6754.86 6760.22 2.33 0.94 0.58 NA NA 2302.11 79.85 SD 1109.751109.06 0.82 0.11 0.38 NA NA 1220.38 13.12

Following an IV combo administration of linezolid and compound 10 at anominal dose of 5 mg/kg for each, the mean±SD value of systemicclearance for linezolid was 0.59±0.03 L/hr/kg, which corresponded to17.82% of rat hepatic blood flow (3.31 L/hr/kg). The mean±SD value ofhalf-life (T_(1/2)) for linezolid was 1.03±0.05 hr.

Following an IV combo administration of linezolid and compound 10 at anominal dose of 5 mg/kg for each, the mean±SD values of C_(max) (at 5minutes after dosing) and AUC_((O-∞)) for linezolid was 5646.60±476.51μg/L and 8459.54±439.14 hr*μg/L. The volume of distribution at terminalphase was 0.88±0.08 L/kg, which corresponded to 131.34% of the totalbody water (0.67 L/kg) in the rats.

Following an oral combo administration of linezolid and compound 10 at anominal dose of 5 mg/kg for each, the mean±SD values of C_(max) andT_(max) for inezolid were 2302.11±1220.38 μg/L and 0.58±0.38 hr,respectively; the mean±SD values of AUC_((0-∞)) and half-life (T_(1/2))were 6760.22±1109.06 hr*μg/L and 0.94±0.11 hr, respectively. The mean±SDvalue of bioavailability for inezolid was 79.85±13.12%.

Pharmacokinetics of Compound 10 after Combinatory Administration

The individual and average concentration-time data of compound 10following intravenous and oral administration compound 10 in combinationwith linezolid are listed in Table 4 and shown in FIGS. 2A-2C. Selectednoncompartmental pharmacokinetic parameters following intravenous andoral dose are listed in Table 5.

TABLE 4 Plasma Concentration of Compound 10 in Male Rats FollowingIntravenous and Oral Administration in Combo with Linezolid Time (hr)Plasma Concentration (ng/mL) IV-5 mg/kg R7 R8 R9 Mean SD 0 BLQ BLQ BLQNA NA 0.083 6239.85 5226.29 6160.63 5875.59 563.70 0.25 4729.24 4608.045155.86 4831.05 287.75 0.5 3590.16 4254.51 4412.69 4085.79 436.45 13305.80 2745.30 2985.25 3012.12 281.21 2 1517.70 1452.58 1736.63 1568.97148.80 4 319.18 368.42 438.89 375.50 60.17 6 70.89 70.76 88.03 76.569.93 8 15.94 29.51 25.09 23.51 6.92 10 0.00 7.06 9.53 5.53 4.95 12 BLQBLQ BLQ NA NA 24 BLQ BLQ BLQ NA NA PO-5 mg/kg R10 R11 R12 Mean SD 0 BLQBLQ BLQ NA NA 0.083 3177.06 913.00 887.24 1659.10 1314.65 0.25 3577.651842.44 1122.93 2181.01 1261.90 0.5 3586.70 2137.40 1218.21 2314.101194.09 1 2683.05 2253.76 1281.26 2072.69 718.22 2 1649.99 1843.141017.10 1503.41 432.09 4 430.42 861.28 682.57 658.09 216.47 6 89.36229.10 467.14 261.87 191.01 8 13.39 52.04 160.20 75.21 76.10 10 7.9023.83 50.81 27.51 21.69 12 0.00 0.00 9.71 3.24 5.61 24 BLQ BLQ BLQ NA NA

TABLE 5 Selected Pharmacokinetics Parameters of Linezolid in RatsFollowing Intravenous and Oral Administration in Combo with Compound 10AUC_((0-t)) AUC_((0-∞)) MRT_((0-∞)) t_(1/2z) T_(max) V_(z) CL_(z)C_(max) F μg/L * hr μg/L * hr hr hr hr L/kg L/hr/kg μg/L % IV-5 mg/kg R18978.23 8979.14 1.30 0.83 0.083 0.67 0.56 6239.85 R2 8631.63 8634.331.39 1.00 0.083 0.84 0.58 5226.29 R3 9736.59 9750.85 1.42 1.04 0.0830.77 0.51 6160.63 mean 9115.48 9121.44 1.37 0.96 0.083 0.76 0.55 5693.46SD 565.13 571.70 0.06 0.11 0 0.09 0.04 660.68 PO-5 mg/kg R4 8049.618061.08 1.59 1.01 0.50 NA NA 3586.70 88.25 R5 8090.94 8096.42 2.32 1.051.00 NA NA 2253.76 88.70 R6 6019.61 6034.82 3.19 1.09 1.00 NA NA 1281.2665.99 mean 7386.72 6939.38 2.37 1.05 0.83 NA NA 2373.91 80.98 SD 1184.133365.36 0.80 0.04 0.29 NA NA 1157.41 12.98

Following an IV combo administration of compound 10 and linezolid at anominal dose of 5 mg/kg for each, the mean±SD value of systemicclearance for compound 10 was 0.55±0.04 L/hr/kg, which corresponded to16.62% of rat hepatic blood flow (3.31 L/hr/kg). The mean±SD value ofhalf-life (T_(1/2)) for compound 10 was 0.96±0.11 hr.

Following an IV combo administration of compound 10 and linezolid at anominal dose of 5 mg/kg for each, the mean±SD values of C_(max) (at 5minutes after dosing) and AUC_((0-∞)) for compound 10 was 5693.46±660.68μg/L and 9121.44±571.70 hr*μg/L. The volume of distribution at terminalphase was 0.76±0.09 L/kg, which corresponded to 113.43% of the totalbody water (0.67 L/kg) in the rats.

Following an oral combo administration of compound 10 and linezolid at anominal dose of 5 mg/kg for each, the mean±SD values of C_(max) andT_(max) for compound 10 were 2373.91±1157.41 μg/L and 0.83±0.29 hr,respectively; the mean±SD values of AUC_((0-∞)) and half-life (T_(1/2))were 6939.38±3365.36 hr*μg/L and 1.05±0.04 hr, respectively. The mean±SDvalue of bioavailability for compound 10 was 80.98±12.98%.

CONCLUSIONS

Following combo IV injection of compound 10 with linezolid, the meanvalues of systemic clearance and half-life for linezolid were 0.59L/hr/kg and 1.03 hr, respectively; the mean value of V, was 0.88 L/kg.The mean value of bioavailability after oral administration forlinezolid was 79.85%.

Following combo IV injection of compound 10 with linezolid, the meanvalues of systemic clearance and half-life for compound 10 were 0.55L/hr/kg and 0.96 hr, respectively; the mean value of V_(z) was 0.76L/kg. The mean value of bioavailability after oral administration forcompound 10 was 80.98%.

A graph showing the mean plasma concentration of linezolid and compound10 over time following intravenous injection of a combination oflinezolid and compound 10 is shown in FIG. 3. A graph showing the meanplasma concentration of linezolid and compound 10 over time followingoral administration of a combination of linezolid and compound 10 isshown in FIG. 4.

Example 4 Mitochondria Toxicity Study

HepG2 cells were seeded at 50,000 cells per well in 6-well plates andgrown in High-Glucose DMEM in the presence of 6 different concentrationsof compound (100 μM, 10 μM, 1 μM, 100 nM, 10 nM and 1 nM). Eachconcentration was tested in triplicate. Cells were also grown in thecorresponding DMSO concentrations present in each of the treatments(5×10⁻¹%, 5×10⁻²%, 5×10⁻³%, 5×10⁻⁴%, 5×10⁻⁵%, 5×10⁻⁶%).

The medium with the compound was changed after 72 hours of treatment andkept for further analysis.

When the cells reached an average of 4 population doublings in thecompound, they were trypsinized, centrifuged and washed with phosphatebuffered saline. The cells were solubilized in 1.5% laurylmaltoside (in25 mM Hepes, 100 mM NaCl, pH 7.4), centrifuged at 25,000 g for 20minutes and supernatants kept for assay.

Enzyme quantity from each well was assessed with duplicate dipsticks.Each dipstick was loaded with 2 μg of solubilized protein to determinethe levels of Complex IV (a mtDNA-encoded protein), and Frataxin (anuclear DNA-encoded protein). Extracts were then stored at −80° C. forfurther analysis.

The amount of enzymes captured on the dipstick was determinedquantitatively with a Hamamatsu Immunochromato Reader. The absorbancesignal of two dipsticks measuring enzyme quantity from the same well wasaveraged (CV<1%) and the means for each triplicate treatment werenormalized by interpolation against an assay specific calibration curve.

Complex IV/Frataxin Ratios were determined for each triplicate treatmentfrom interpolated values. Triplicate ratios for each treatmentconcentration were analyzed using a non-linear regression curve in GraphPad (Log[inhibitor] vs. response—variable slope). Results are shown inFIGS. 5A-5B. IC₅₀ values for linezolid and compound 10 are 7.8 and 9.8μM, respectively.

In conclusion, the mitochondria toxicity for compound 10 is comparableto that of linezolid.

While this invention has been particularly shown and described withreferences to example embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

1. A process for the preparation of a compound of the formula (I) or asalt thereof, the process comprising reacting a compound of Formula (II)with an acid to form the compound of Formula (I) or a salt thereof:

wherein: R¹ is —H, —OH, —NO, —NH₂, —NHR^(a), —N(R^(a))₂,—C(═O)NR^(c)R^(d), —C(═O)OR^(g), -phthalimido, —SO₂—R^(b), or a groupselected from alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl,cycloalkyl, heterocycloalkyl, cycloalkylalkyl, heterocycloalkylalkyl,wherein the alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, cycloalkyl,heterocycloalkyl, cycloalkylalkyl, and heterocycloalkylalkyl are eachindependently optionally substituted with one or more groups selectedfrom halogen, C₁₋₆ alkyl, —OR^(e), —C(═O)OR^(e), —C(═O)R^(e), —NO₂, —CN,—NH₂, —NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(e), —C(═O)NR^(c)R^(d),—S(O)R^(e), —S(O)₂R^(e), —SR^(e), and —SO₂NR^(c)R^(d), wherein each C₁₋₆alkyl is optionally substituted with one or more groups selected fromhalogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆haloalkoxy; each R^(a) is independently an alkyl optionally substitutedwith halogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl or C₁₋₆haloalkoxy; R^(b) is alkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl,each of which is optionally substituted with one or more groups selectedfrom halogen, C₁₋₆ alkyl, —OR^(e), —C(═O)OR^(e), —C(═O)R^(e), —NO₂, —CN,—NH₂, —NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(e), —C(═O)NR^(c)R^(d),—S(O)^(e), —S(O)₂R^(e), —SR^(e), and —SO₂NR^(c)R^(d), wherein each C₁₋₆alkyl is optionally substituted with one or more groups selected fromhalogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆haloalkoxy; R^(c) and R^(d) are each independently —H or alkyloptionally substituted with one or more groups selected from halogen,C₁₋₆ alkyl, —OR^(e), —C(═O)OR^(e), —C(═O)R^(e), —NO₂, —CN, —NH₂,—NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(e), —C(═O)NR^(c)R^(d), —S(O)R^(e),—S(O)₂R^(e), —SR^(e), and —SO₂NR^(c)R^(d), wherein each C₁₋₆ alkyl isoptionally substituted with one or more groups selected from halogen,C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆ haloalkoxy; R^(e)is —H or alkyl optionally substituted with one or more groups selectedfrom halogen, C₁₋₆ alkyl, —OR^(f), —C(═O)OR^(f), —C(═O)R^(f), —NO₂, —CN,—NH₂, —NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(f), —C(═O)NR^(c)R^(d),—S(O)R^(f), —S(O)₂R^(f), —SR^(f), and —SO₂NR^(c)R^(d), wherein each C₁₋₆alkyl substituent is optionally substituted with one or more groupsselected from halogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl andC₁₋₆ haloalkoxy; R^(f) is alkyl, cycloalkyl, heterocycloalkyl, aryl orheteroaryl; R^(g) is alkyl optionally substituted with one or moregroups selected from halogen, C₁₋₆ alkyl, —OR^(f), —C(═O)OR^(f),—C(═O)R^(f), —NO₂, —CN, —NH₂, —NHR^(a), —N(R^(a))₂, —NR^(c)C(═O)R^(f),—C(═O)NR^(c)R^(d), —S(O)R^(f), —S(O)₂R^(f), —SR^(f), and—SO₂NR^(c)R^(d), wherein each C₁₋₆ alkyl substituent is optionallysubstituted with one or more groups selected from halogen, C₁₋₆ alkyl,C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl and C₁₋₆ haloalkoxy; and R⁴, R^(4′), R⁵and R^(5′) are each independently —H or C₁₋₄ alkyl optionallysubstituted with one or more halogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆haloalkyl, or C₁₋₆ haloalkoxy.
 2. The process of claim 1, furthercomprising reacting a compound of Formula (III)

with a reducing agent to form a compound of formula (II) or a saltthereof, wherein each R² is D, —OH, or —O(alkyl).
 3. The process ofclaim 2, wherein R² is —OH, or —O(alkyl).
 4. The process of any one ofclaims 1 to 3, wherein the deuterium enrichment at each positiondesignated as deuterium in the compound of Formula (I) is at least about85%.
 5. The process of any one of claims 1 to 4, wherein the acid is aLewis acid or a Bronsted acid.
 6. The process of claim 2 or 3, whereinthe reducing agent is selected from diborane-d₆ (B₂D₆), DSiCl₃, Et₃SiD,diisobutylaluminum deuteride (DIBAL-D), LiAlD₄, LiBD₄, and NaBD₄.
 7. Theprocess of any one of claims 1 to 6, wherein R¹ is benzyl, —SO₂-aryl, or—SO₂-heteroaryl.
 8. The process of claim 1, further comprising the stepof removing R¹ from a compound represented by Structural Formula (I)when R¹ is a group other than —H to form an optionally substitutedmorpholine-2,2,6,6-d₄ represented by Structural Formula (Ia) or a saltthereof:


9. The process of claim 8, wherein R¹ is benzyl and the benzyl group isremoved under hydrogenation conditions.
 10. The process of any one ofclaims 1-9, wherein R⁴, R^(4′), R⁵ and R^(5′) are all —H.
 11. A compoundof Formula (II):

or a salt thereof, wherein each of R¹, R⁴, R^(4′), R⁵, and R^(5′) is asdefined in claim
 1. 12. The compound of claim 11, wherein the deuteriumenrichment at each position designated as deuterium is at least about85%.
 13. The compound of claim 12, wherein R⁴, R^(4′), R⁵ and R^(5′) areeach —H; R¹ is benzyl; and the deuterium enrichment at each positiondesignated as deuterium is 95%.
 14. A compound represented of Formula(I):

or a salt thereof, wherein each of R¹, R⁴, R^(4′), R⁵, and R^(5′) is asdefined in claim 1; and wherein the deuterium enrichment at eachposition designated as deuterium is at least about 85%.
 15. The compoundof claim 14, wherein each of R⁴, R^(4′), R⁵ and R^(5′) is hydrogen, or asalt thereof; and wherein the deuterium enrichment at each positiondesignated as deuterium is at least about 95%.
 16. The compound of claim14 or 15, wherein R¹ is —H, benzyl, —SO₂-aryl, or —SO₂-heteroaryl. 17.The compound of claim 15, wherein R¹ is benzyl.
 18. The compound ofclaim 14, wherein R^(e) is alkyl optionally substituted with one or moregroups selected from halogen, C₁₋₆ alkyl, —NO₂, —CN, —NH₂, —NHR^(a),—N(R^(a))₂, —C(═O)NR^(c)R^(d), and —SO₂NR^(c)R^(d), wherein each C₁₋₆alkyl substituent is optionally substituted with one or more groupsselected from halogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, —OH, C₁₋₆ haloalkyl andC₁₋₆ haloalkoxy.
 19. A compound represented by the following structuralformula:

or a salt thereof, wherein the deuterium enrichment at each positiondesignated as deuterium is at least about 95%.
 20. A pyrogen-freepharmaceutical composition comprising the compound of claim 19; and apharmaceutically acceptable carrier.
 21. A composition comprising thecompound of claim 19; and a pharmaceutically acceptable carrier for usein treating a bacterial infection or a fungal disorder in a subject inneed thereof.
 22. The composition of claim 21, wherein the bacterialinfection is caused by a bacteria selected from Enterococcus faecium,Staphylococcus aureus, Streptococcus agalactiae, Streptococcuspneumoniae, Streptococcus pyrogenes, Enterococcus faecalis,Staphylococcus epidermidis, Staphyloccocus haemolyticus, and Pasteurellamultocida.
 23. The composition of claim 21, wherein the bacterialinfection or fungal disorder is selected from a Gram-positive bacterialinfection; Vancomycin-resistant Enterococcus faecium infection;nosocomial pneumonia due to Staphylococcus aureus and Streptococcuspneumoniae; complicated skin and skin structure infections caused byStaphylococcus aureus, Streptococcus pyogenes, or Streptococcusagalactiae; uncomplicated skin and skin structure infections caused byStaphylococcus aureus or Streptococcus pyogenes; and community-acquiredpneumonia caused by Streptococcus pneumoniae or Staphylococcus aureus.24. A method of treating a bacterial infection or a fungal disorder in asubject in need thereof comprising the step of administering to thesubject in need thereof the composition of claim
 20. 25. The method ofclaim 24, wherein the bacterial infection is caused by a bacteriaselected from Enterococcus faecium, Staphylococcus aureus, Streptococcusagalactiae, Streptococcus pneumoniae, Streptococcus pyrogenes,Enterococcus faecalis, Staphylococcus epidermidis, Staphyloccocushaemolyticus, and Pasteurella multocida.
 26. The method of claim 25,wherein the bacterial infection or fungal disorder is selected from aGram-positive bacterial infection; Vancomycin-resistant Enterococcusfaecium infection; nosocomial pneumonia due to Staphylococcus aureus andStreptococcus pneumoniae; complicated skin and skin structure infectionscaused by Staphylococcus aureus, Streptococcus pyogenes, orStreptococcus agalactiae; uncomplicated skin and skin structureinfections caused by Staphylococcus aureus or Streptococcus pyogenes;and community-acquired pneumonia caused by Streptococcus pneumoniae orStaphylococcus aureus.
 27. The method of any one of claims 24-26,further comprising the step of administering to the subject in needthereof a second therapeutic agent selected from gentamicin, tobramycin,aztreonam, cefazolin, ceftazidime, piperacillin, ciprofloxacin,ofloxacin, levofloxacin, celecoxib, and rofecoxib.
 28. The method ofclaim 24, wherein the infection is an infection of the eye ortuberculosis.
 29. The method of claim 24, wherein the infection is aninfection selected from the group consisting of diabetic footinfections, nocardiosis, endophthalmitis, keratitis, conjunctivitis, andimpetigo.
 30. A compound represented by a structural formula selectedfrom:

or a salt thereof, wherein the deuterium enrichment at each positiondesignated as deuterium is at least about 95%.